1. Field of the Invention
This invention relates to an image-inverting prism device with double use for a telescope, particularly to one usable for two kinds of different diameter lenses of a telescope.
2. Description of the Prior Art
In spite of a refracting or a reflective telescope, images seen through the lenses are inverted, so in order to get rid of the uncomfortable feeling in viewing through a telescope, an image-inverting prism is added between the lenses. Further, a small lens and a large lens with different focus distances are used for magnifying an object to different enlarged sizes. The small lens has a diameter 0.965 inch and the large viewing lens 1.25 inch. Makers not only manufacture the two kinds of lenses for consumers, but also have to manufacture two kinds of image-inverting prisms to correspond to the small and the large lenses. As for the image-inverting prism, it contains a prism for inverting the image, resulting in a high cost. So retailers of telescopes have to store two different kinds of small and large lenses and image-inverting prisms for consumer to select, increasing expense for the retailers and for consumers.